Misty Lackey's work is well-loved by fanfic writers; this allows them to come in from the cold and produce their work (which celebrates her work) without fear of legal reprisals. Good move all around (and my agent, Russ Galen, is a smart cookie!).
What this means is: NO, you cannot make money on it. NO, you cannot self-publish a fanfiction novel of Valdemar (or any of my other stuff) and try and sell it on Amazon. And NO, I still am not going to read it, because I am already so far behind on my research reading I barely have time to read that.News: Concerning Fanfiction: (Thanks, Chris!)
But YES, you may write and post away, folks, so long as you license it as derivative and under Creative Commons. If it is anything other than PG-13, please take all the proper precautions to stick it somewhere that innocent souls won't be corrupted. Do not scare the children or the horses. Have fun!
I write books. My latest is a YA science fiction novel called Homeland (it's the sequel to Little Brother). More books: Rapture of the Nerds (a novel, with Charlie Stross); With a Little Help (short stories); and The Great Big Beautiful Tomorrow (novella and nonfic). I speak all over the place and I tweet and tumble, too.